How long to have photographer

I'm clueless as to how long to have the photographer...I was thinking start to finish, but that get's really pricey...I have a shot sheet, but it's not helping me to figure out the right amount of time...

i have mine for 5 hours. starting about an hour before the ceremony with getting ready shots, the ceremony, the family photos after, shots of us alone while everyone else is at cocktail hour. we will join the cocktail hour for the last 15 mins or so, and then 2 hours of reception coverage. we didnt want to be paying a photog for drunk shots of our fam & friends, figured we could get enough of those from peoples cameras.

I guess you need to decide whats important. If you want pics of you getting ready, the ceremony, the reception, etc that may be start to finish. Personally I dont care about pics of getting ready so that got rid of that. So if everything is on your must have shots of list then you may be for the long bill.